Cardiopulmonary resuscitation (CPR) is a well-known and valuable method of first aid used to resuscitate people who have suffered from cardiac arrest. CPR requires repetitive chest compressions to squeeze the heart and the thoracic cavity to pump blood through the body. Artificial respiration, such as mouth-to-mouth breathing or a bag mask apparatus, is used to supply air to the lungs. When a first aid provider performs manual chest compression effectively, blood flow in the body is about 25% to 30% of normal blood flow. However, even experienced paramedics cannot maintain adequate chest compressions for more than a few minutes. Hightower, et al., Decay In Quality Of Chest Compressions Over Time, 26 Ann. Emerg. Med. 300 (September 1995). Thus, CPR is not often successful at sustaining or reviving the patient. Nevertheless, if chest compressions could be adequately maintained, then cardiac arrest victims could be sustained for extended periods of time. Occasional reports of extended CPR efforts (45 to 90 minutes) have been reported, with the victims eventually being saved by coronary bypass surgery. See Tovar, et al., Successful Myocardial Revascularization and Neurologic Recovery, 22 Texas Heart J. 271 (1995).
In efforts to provide better blood flow and increase the effectiveness of bystander resuscitation efforts, various mechanical devices have been proposed for performing CPR. In one variation of such devices, a belt is placed around the patient's chest and an automatic chest compression device tightens the belt to effect chest compressions. Our own patents, Mollenauer et al., Resuscitation device having a motor driven belt to constrict/compress the chest, U.S. Pat. No. 6,142,962 (Nov. 7, 2000); Bystrom et al., Resuscitation and alert system, U.S. Pat. No. 6,090,056 (Jul. 18, 2000); Sherman et al., Modular CPR assist device, U.S. Pat. No. 6,066,106 (May 23, 2000); and Sherman et al., Modular CPR assist device, U.S. Pat. No. 6,398,745 (Jun. 4, 2002); and our application Ser. No. 09/866,377 filed on May 25, 2001, our application Ser. No. 10/192,771, filed Jul. 10, 2002 and our application Ser. No. 12/726,262, filed Mar. 17, 2010 show chest compression devices that compress a patient's chest with a belt. Each of these patents or applications is hereby incorporated by reference in their entireties.
Since seconds count during an emergency, any CPR device should be easy to use and facilitate rapid deployment of the device on the patient. Our own devices are easy to deploy quickly and may significantly increase the patient's chances of survival.
One important aspect of such devices is the need for small, powerful yet reliable power supply to power the device. It is not uncommon for CPR to be administered for at least thirty minutes. Thus, the power supply must be capable of delivering sufficient energy to the motor driving the compression device for at least that length of time. Moreover, the power supply must be relatively light weight, so as to enhance portability of the chest compression device, yet it must deliver its power for an extended period of time without significant voltage or current drop off to ensure consistency of compression throughout the treatment period.
Various approaches to providing the type of high current power cell battery needed to power a mechanical compression device have been designed. As more efficient battery designs and chemistries have been used, the need to carefully manage the charging and discharging of the battery has arisen. To meet this need, complex battery management circuitry has been designed, including the use of processors, memory, and other components. All of these components need to fit within the confines of the battery casing designed for use in a piece of equipment to be powered.
To prevent inadvertent shorting of the battery terminals, one approach that has shown promise is to electrically isolate the battery cells from the terminals unless the battery is properly inserted into a device to be powered, a charger, or other authorized device. Such isolation requires the use of some type of switch which may be controlled by the battery management software and hardware.
What has been needed, and heretofore unavailable, is a light weight, reliable battery pack capable of delivering high current output to power, for example, a medical device. Such a battery should also include a mechanism and/or circuitry to prevent rapid high current discharge of the battery in the event of accidental shorting of the battery terminals. The present invention satisfies these, and other needs.